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       Transmission Control Protocol        User Datagram Protocol
Well-known ports = 0 to 1,023
  Registered ports = 1,024 to 49,151
     Dynamic ports = 49,152 to 65,535

A connection between two computers uses a socket.
A socket is the combination of IP address plus port.

Stream Control Transmission Protocol (SCTP)
Datagram Congestion Control Protocol (DCCP)
Reliable Unreliable
Connection-oriented Connectionless
Segment retransmission
and flow control through
windowing (Slider acknowledgment)
No windowing or
Segment sequencing No sequencing
  Acknowledge segments     No acknowledgement

All ports support TCP/UDP protocols. Sometimes Protocols use two ports, one for control configuration
and one for data transfer.   In some instances, control and transfer are conveyed on the same port.
Application specific as to TCP or UDP implementation, i.e. Ė (Port 7) Ping=UDP, Traceroute=TCP

= Noteworthy  
= File Transfer  
= Encrypted/SSL  
= Email  
= Remote Access  
7 ECHO Echo   TCP UDP   Server sends back an identical
copy of the data it received
20,21 FTP File Transport Protocol
 ⦁ 20 for data transfer
 ⦁ 21 for control commands
  TCP   SCTP Provides the ability to easily relocate
files from one system to another
22 SSH Secure Shell TCP UDP SCTP Uses a cryptographic (encrypted) protocols
operating securely over an unsecured
network in a client-server architecture
23 Telnet Telnet protocol - unencrypted
text communications
  TCP UDP   Connect to routers (TCP); designed to provide a bi-
directional connection with other devices (UDP)
25 SMTP Simple Mail Transport Protocol TCP     Mail relay - used for sending email
37 Time Provides remote timing statís
of internal processing events
  TCP UDP   Security Concerns: Gives remote attacker
info on hostís internal processing load
43 WhoIs WHOIS directory service   TCP UDP   nicname
47 GRE Generic Routing Encapsulation   X X   Cisco tunneling protocol encapsulating protocols
inside virtual point-to-point links over an IP network
49 TACACS Terminal Access Controller
Access-Control System
  TCP UDP   Login Host protocol (AAA)
TACACS+ Encrypts the full content of each packet TCP   TACACS+ and RADIUS have
generally replaced TACACS (AAA)
Proprietary - CISCO
53 DNS Domain Name System   TCP UDP   Dangerous poisoning - attacks
TCP for Zone Transfers - UDP for Queries
67 DHCP Dynamic Host Configuration Protocol
(BOOTPS) - server
  UDP   Issues automatic IP services; Uses
DORA = Discover, Offer, Request, Acknowledge
if DHCP unavailable, Automatic Private IP
Addressing (APIPA) used - 169.254.x.y
68 DHCP (BOOTPC) - client   UDP  
69 TFTP Trivial File Transport Protocol     UDP   File transfer without the session establishment
80 HTTP Hypertext Transfer Protocol   TCP   SCTP Main protocol that is used by web browsers
88 KERBEROS A three-headed dog who guarded
the gates of Hades. Represents a
client, a server, and a Key
  TCP UDP   Authenticating agent, time stamped.
Uses secret-key asymmetric cryptography to
authenticate client-server applications.
110 POP3 Post Office Protocol version 3   TCP     Basic email retrieval; Make sure to set
"save on server," - not default setting,
- deletes off server once downloaded
119 NNTP Network News Transfer Protocol   TCP UDP   For the USENET discussion system
123 NTP Network Time Protocol     UDP   Synchronized down to the milisecond
with U.S. Naval Observatory clocks
137 NETBIOS Network Basic Input/Output System   UDP   Naming service. Allows applications on
different computers to communicate
within a local area network (LAN)
138 NETBIOS (NetBIOS) datagram service   UDP  
139 NETBIOS NetBIOS session service   TCP  
143 IMAP4 Internet message access protocol ver. 4   TCP   Recieving mail - Multiple client use
156 SQL Server sqlsrv   TCP UDP   SQL Service
161 SNMP
Simple Network Management Protocol
SNMPv3 1st to encyrpt
  UDP   Monitors information to best change
device behavior; cable modems, routers,
switches, servers, workstations, printers,
etc., uptime, model #, insecure by default
162 SNMP Trap Simple Network Management Protocol Trap   TCP UDP   Collection of informantion
194 IRC Internet Relay Chat   TCP   Designed for group communication
in discussion forums, called channels
201 Apple Talk AppleTalk Routing Maintenance   TCP UDP   X
389 LDAP Lightweight Directory Access Protocol   TCP   Remote connections, accesses and maintains
distributed hierachical directory information
427 SLP Service Location Protocol   TCP UDP   Application = svrloc
443 HTTPS Hypertext Transfer Protocol Secure TCP   SCTP Uses SSL, Secure Sockets Layer encryption
SSL VPN Secure Sockets Layer virtual
private network (SSTP)
445 SMB Service Message Block   TCP   Microsoft-DS Over TCP/IP - Printers
CIFS (Common Internet File System)
464 KPASSWD Kerberos password and
key changing services
465 SMTPS Simple Mail Transfer Protocol Secured TCP UDP   SMTP over SSL - should no longer be used
500 IPSEC IP Security   TCP UDP   ISAKMP / IKE - Internet Key Exchange
514 SYSLOG Standard for message logging   UDP   Capture all IDs logs
520 RIP Routing Information Protocol   UDP   Used to advertise routing information among
routers and communicate optimal paths
546 DHCPv6 DHCPv6 - client   TCP UDP   Dynamic Host Configuration Protocol
547 DHCPv6 DHCPv6 - server   TCP UDP  
548 AFP Apple Filing Protocol   TCP UDP   AFP over TCP
569 MSN ms-rome   TCP UDP   Microsoft Rome Game Port
587 SMTPS Message Submission   TCP UDP   Default Mail Message Submission Agent (MSA)
Uses TLS encryption
636 LDAPS Secure LDAP TCP   LDAP over SSL
989,990 FTPS  ⦁ 989 = (data) over TLS/SSL
 ⦁ 990 = (control) over TLS/SSL
TCP UDP   over SSL or TLS
992 TELNETS Bi-directional communications, Secured TCP UDP   End-to-end communications after SSL/TLS
is set up; user's data sent bi-directionally
993 IMAPS Internet Message
Access Protocol Secured
TCP UDP   Encypted over SSL/TLS
995 POP3S Connect using POP3 securely TCP     Over Secure Sockets Layer (SSL) -TLS
1433 MS SQL Microsoft Structured Query Language   TCP   Standard for database manipulation
1434 MS SQL Microsoft Structured Query Language   UDP  
1701 L2TP Layer 2 Tunneling Protocol   UDP   Requires public key/utilizes IPSec
May be blocked by NAT
1720 H.323 H.323 call setup TCP UDP   Voice over IP (VoIP) signaling,
one of the earliest used
1723 PPTP Point-to-Point Tunneling Protocol   TCP UDP   One of the oldest VPN protocals
- Does not use certificates
1812 RADIUS Remote Authentication
Dial-in User Service
  UDP   Old technology, AAA dial up for
Authentication Authorize Accounting
2049 NFS Network File System   TCP UDP SCTP Used by UNIX clients for file access
2427 MGCP Media Gateway Control Protocol   TCP UDP   X??
2727 MGCP Media Gateway Control Protocol   TCP UDP   Callagent
3389 RDP Remote Desktop Protocol   TCP   Remote Desktop
5004 RTP Real-Time Transport Protocol   TCP UDP dccp VoIP and/or video apps
5005 RTP RTP control Protocol   TCP UDP dccp VoIP and/or video apps
5060 SIP Session Initiation Protocol TCP UDP SCTP VoIP and/or video apps
unencrypted signaling traffic (RTP)
5061 SIP Session Initiation Protocol TCP SCTP VoIP and/or video apps
encrypted traffic (SRTP)
5900 VNC Virtual Network Computing   TCP ?   Client/server graphical desktop sharing system
that uses the Remote Frame Buffer protocol
(RFB) to remotely control another computer
9100 JETDIRECT Allows computer printers to
be directly attached to a LAN
  TCP UDP   Printer on
HP network printing service
33434 Traceroute Traceroute network tracking tool   TCP UDP
33435 Traceroute Mtrace-multicast traceroute   UDP
X X X   X X X X

Common Network Ports - Professor Messer       PowerCert Port Forwarding Video

Iana.org - Port Number Assignments       VPN Ports & Port Forwarding

Common Ports - MIT


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